This invention relates to a laser heating apparatus for heating a thin film forming substrate to an elevated temperature in a thin film manufacturing process.
In the case of forming a thin film on a semiconductor wafer and, inter alia, forming an oxide film on a substrate in a vacuum film forming apparatus designed to cause such a thin film to epitaxially grow, oxygen gas is introduced into a vacuum chamber of the film forming apparatus and is brought under a pressure of 10xe2x88x922 to 10xe2x88x924 Torr. Also by heating the substrate to an elevated temperature, adjustment is made of film forming conditions.
To precisely position the substrate while heating it in such vacuum film forming apparatus in a manner as mentioned above, it has been the conventional practice that a small, electrically energizable heater is placed in a substrate setting area on a specimen precision mounting table (such as goniometer). Then, by energizing the heater with electric current to cause it to emit heat, the substrate is indirectly heated with heat so emitted.
As an alternative, a method has also been known that draws electric current directly through the substrate fixed on the specimen mounting table, thereby causing the substrate itself to emit heat.
In such conventional apparatus, however, especially of the type using the small heater, the maximum attainable heating temperature is limited up to as low as 800xc2x0 C. Then, efficient heating cannot be achieved, and it is not necessarily easy to establish desired film forming conditions. In addition, there always exists the likelihood for the heater to burn off, making its use in an oxidizing atmosphere impossible. Also, the method of flowing current through the specimen substrate is only applicable to those substrates such as silicon substrates that can carry electric current, and must therefore have limited applicability.
Moreover, both of these methods or apparatus mentioned above requires heating by direct or indirect application of an electric current, which necessarily causes a magnetic field to build up. Such occurrence of a magnetic field gives rise to problems, when using an analysis that involves an analysis by using a low energy ion or electron beam, such as of affecting the precision of analysis by the magnetic field causing the traveling beam to deflect.
It is accordingly an object of the present invention to provide a laser heating apparatus that is capable of efficiently and properly heating a specimen substrate in a vacuum apparatus.
In order to achieve the object mentioned above, there is provided in accordance with the present invention, a laser heating apparatus for heating a thin film forming substrate, characterized in that a thin film forming substrate set in position on a substrate supporting mechanism in a vacuum chamber of a film forming apparatus is irradiated with a laser light so as to be heated to a predetermined temperature.
The apparatus mentioned above allows a substrate to be heated to and at a high temperature in an extremely short period of time. Further, using a laser light as means for heating the substrate permits the apparatus to be used even in an oxidizing atmosphere and also even an insulating substrate to be effectively heated. Also, freeing a heat source in a region of the substrate from current passage prevents generation of a magnetic noise and allows analysis using a low energy charged particle beam to be conducted properly.
The said substrate supporting mechanism can be a substrate supporting mechanism that is capable of positioning the said substrate in three orthogonal axial directions along an X-, a Y- and a Z-axis, and is also capable of so-called xe2x80x9cU-centricxe2x80x9d rotation. This specific arrangement being a mechanism that is capable of xe2x80x9cU-centricxe2x80x9d rotation has the advantage that tilting the substrate by the substrate supporting mechanism does not alter the conditions for irradiating the substrate with the laser light and does not alter the temperature of the substrate.
This specific arrangement permits only the substrate to be selectively heated.
Also, in a further preferred form of the laser heating apparatus according to the present invention, the said optical fiber is sheathed with a jacket tube whose interior is vacuum drawn or evacuated.
So constructed, the laser heating apparatus of the present invention can be used with a high vacuum apparatus.
Also, in a further preferred specific form of embodiment of the laser heating apparatus according to the present invention, the said optical fiber at an end thereof opposite to its outlet end is fastened to the said jacket tube by means of a fiber chuck and is fitted in a fitting bore of a flange and fastened thereto by means of a ferrule. So constructed, the laser heating apparatus according to the present invention can establish end-face coupling by coupling together the end face of the optical fiber leading from the laser generator placed outside of the vacuum chamber and the end face of the optical fiber located inside the vacuum chamber by connector, and thus permits introducing the laser light into the vacuum chamber without materially affecting a vacuum attained therein.
Further, in another preferred form of the laser heating apparatus according to the present invention, the laser light from the outlet end of the said optical fiber is radiated via a reflecting mirror onto the substrate.
This specific arrangement permits the position of irradiation with the laser beam to be altered.
Also, in another preferred form of embodiment of the laser heating apparatus according to the present invention, the laser light is a Nd:YAG laser light.
This specific arrangement allows the substrate to be heated to and at a high temperature in an extremely short period of time.
Further, in another specific form of embodiment of the laser heating apparatus, there is included a substrate holder for holding a substrate, the substrate holder having slit orifices formed so as to surround the substrate supported thereby.
This specific arrangement permits the substrate to be heated efficiently by preventing diffusion of heat and increasing temperature uniformity.
Also, in another preferred specific form of embodiment of the laser heating apparatus according to the present invention, there is included a substrate holder for holding a substrate, the substrate holder having an area on which the laser light is incident, and which area is composed of a material that is high in laser light absorbing power.
This specific arrangement permits the substrate to efficiently absorb the laser light.
Further, in another preferred specific form of embodiment of the laser heating apparatus according to the present invention, there is included a substrate holder for holding the substrate, the substrate holder having an area on which said laser light is incident, and which area is coated with a material that is a metal oxide or ceramic.
This specific arrangement makes the substrate holder light in weight and yet causes it to absorb the laser light efficiently to heat the substrate.
Also, in another preferred specific form of embodiment of the laser heating apparatus according to the present invention, there is included a substrate holder for holding the substrate, the substrate holder having an area on which the laser light is incident, and which area is formed with a thin film that is composed of a material that is high in laser light absorptivity.
This specific arrangement makes the substrate holder light in weight and yet causes it to absorb the laser light efficiently to heat the substrate.
Further, in yet another specific form of embodiment of the laser heating apparatus according to the present invention, the said coating or thin film material so that it may not be vaporized is protected by a transparent material.
This specific arrangement prevents the material that absorbs the laser light from depletion or degradation.